A measles outbreak in Texas has grown to 90 cases, mostly among unvaccinated children, state health data published Friday shows.

Over the past month, the virus has spread in areas with low vaccination rates, and most of those affected are minors.

An outbreak of measles has struck the South Plains region of Texas, with 90 cases reported since late January, according to the Texas Department of State Health Services (DSHS). The outbreak has affected seven counties in total,